linux-kernel - Re: [PATCH V1] PCI/ASPM: Update saved buffers with latest ASPM configuration

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Date:   Wed, 25 Jan 2023 16:01:15 +0100
From:   "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>
To:     Vidya Sagar <vidyas@...dia.com>, <bhelgaas@...gle.com>,
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        <kai.heng.feng@...onical.com>
CC:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <treding@...dia.com>, <jonathanh@...dia.com>, <kthota@...dia.com>,
        <mmaddireddy@...dia.com>, <sagar.tv@...il.com>
Subject: Re: [PATCH V1] PCI/ASPM: Update saved buffers with latest ASPM
 configuration

On 1/25/2023 2:38 PM, Vidya Sagar wrote:
> Many PCIe device drivers save the configuration state of their respective
> devices during probe and restore the same when their 'slot_reset' hook
> is called through PCIe Error Recovery System.
> If the system has a change in ASPM policy after the driver's probe is
> called and before error event occurred, 'slot_reset' hook restores the
> PCIe configuration state to what it was at the time of probe but not with
> what it was just before the occurrence of the error event.
> This effectively leads to a mismatch in the ASPM configuration between
> the device and its upstream parent device.
> This patch addresses that issue by updating the saved configuration state
> of the device with the latest info whenever there is a change w.r.t ASPM
> policy.
>
> Signed-off-by: Vidya Sagar <vidyas@...dia.com>

If it is a bug fix (which I think it is), a Fixes tag should be present 
here.

If the reporter's names are known, Reported-by tags should be present 
here too.

If anyone except for you has tested this patch, a Tested-by tag should 
be present here.

> ---
>   drivers/pci/pci.h       |  4 ++++
>   drivers/pci/pcie/aspm.c | 40 ++++++++++++++++++++++++++++++++++++++++
>   2 files changed, 44 insertions(+)
>
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 9ed3b5550043..f4a91d4fe96d 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -566,12 +566,16 @@ bool pcie_wait_for_link(struct pci_dev *pdev, bool active);
>   void pcie_aspm_init_link_state(struct pci_dev *pdev);
>   void pcie_aspm_exit_link_state(struct pci_dev *pdev);
>   void pcie_aspm_powersave_config_link(struct pci_dev *pdev);
> +void pci_save_aspm_state(struct pci_dev *dev);
> +void pci_restore_aspm_state(struct pci_dev *dev);
>   void pci_save_aspm_l1ss_state(struct pci_dev *dev);
>   void pci_restore_aspm_l1ss_state(struct pci_dev *dev);
>   #else
>   static inline void pcie_aspm_init_link_state(struct pci_dev *pdev) { }
>   static inline void pcie_aspm_exit_link_state(struct pci_dev *pdev) { }
>   static inline void pcie_aspm_powersave_config_link(struct pci_dev *pdev) { }
> +static inline void pci_save_aspm_state(struct pci_dev *dev) { }
> +static inline void pci_restore_aspm_state(struct pci_dev *dev) { }
>   static inline void pci_save_aspm_l1ss_state(struct pci_dev *dev) { }
>   static inline void pci_restore_aspm_l1ss_state(struct pci_dev *dev) { }
>   #endif
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 53a1fa306e1e..f25e0440d36b 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -151,6 +151,7 @@ static void pcie_set_clkpm_nocheck(struct pcie_link_state *link, int enable)
>   						   PCI_EXP_LNKCTL_CLKREQ_EN,
>   						   val);
>   	link->clkpm_enabled = !!enable;
> +	pci_save_aspm_state(child);
>   }
>   
>   static void pcie_set_clkpm(struct pcie_link_state *link, int enable)
> @@ -757,6 +758,39 @@ static void pcie_config_aspm_l1ss(struct pcie_link_state *link, u32 state)
>   				PCI_L1SS_CTL1_L1SS_MASK, val);
>   }
>   
> +void pci_save_aspm_state(struct pci_dev *dev)
> +{
> +	int i = 0;
> +	struct pci_cap_saved_state *save_state;
> +	u16 *cap;
> +
> +	if (!pci_is_pcie(dev))
> +		return;
> +
> +	save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP);
> +	if (!save_state)
> +		return;
> +
> +	cap = (u16 *)&save_state->cap.data[0];
> +	i++;
> +	pcie_capability_read_word(dev, PCI_EXP_LNKCTL, &cap[i++]);
> +}
> +
> +void pci_restore_aspm_state(struct pci_dev *dev)
> +{
> +	int i = 0;
> +	struct pci_cap_saved_state *save_state;
> +	u16 *cap;
> +
> +	save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP);
> +	if (!save_state)
> +		return;
> +
> +	cap = (u16 *)&save_state->cap.data[0];
> +	i++;
> +	pcie_capability_write_word(dev, PCI_EXP_LNKCTL, cap[i++]);
> +}
> +
>   void pci_save_aspm_l1ss_state(struct pci_dev *dev)
>   {
>   	struct pci_cap_saved_state *save_state;
> @@ -849,6 +883,12 @@ static void pcie_config_aspm_link(struct pcie_link_state *link, u32 state)
>   		pcie_config_aspm_dev(parent, upstream);
>   
>   	link->aspm_enabled = state;
> +
> +	/* Update latest ASPM configuration in saved context */
> +	pci_save_aspm_state(link->downstream);
> +	pci_save_aspm_l1ss_state(link->downstream);
> +	pci_save_aspm_state(parent);
> +	pci_save_aspm_l1ss_state(parent);
>   }
>   
>   static void pcie_config_aspm_path(struct pcie_link_state *link)